System and method for cooling a computer system

ABSTRACT

The invention relates to a system for cooling a computing system, the computing system being cooled using at least two cooling circuits.

FIELD OF THE INVENTION

The invention relates to a system and a method for cooling a computingsystem, in particular for cooling a server farm.

BACKGROUND OF THE INVENTION

Computing systems, in particular server farms comprising a large numberof racks, generate large amounts of heat during operation. For example,a server farm typically has a pure heat output of several kilowatts. Inorder to discharge these large amounts of heat, generally, airconditioners are used which are very energy intensive in operation.

There are approaches known from practice which attempt to use the wasteheat of a computing system to heat a building. However, often such anapproach is not feasible for lack of heatable building surfaces in theproximity, and depending on the climate zone and season it is notsuitable to provide for adequate cooling of an existing computing systemin an building. Moreover, in the summer heating energy for heatingbuildings is often not required.

It is estimated that the energy needed for server farms will increase upto 100 GWh or more in the next few years, with up to 40% of this energybeing attributed to cooling alone.

Conventional computing systems are usually cooled through the airconditioning of the room, and the individual computers release heat tothe ambient air via a fan.

But there are also more recent approaches in which the racks of acomputing system are cooled using a liquid, wherein the cooling air ofthe racks transfers its heat energy to a liquid to be cooled outside therack via a heat exchanger integrated in the rack or arranged adjacent tothe rack.

Another approach is to directly discharge the heat energy from theprocessors using a liquid cooling circuit. A direct discharge of heatenergy is to be understood as a configuration in which liquid-cooledheat sinks are in direct contact with the processors. This method,though it has the advantage that a majority of the generated heat can bedischarged from a small local volume, has not yet been implemented inpractice, at least not on an industrial scale, possibly due to the factthat the technical difficulties associated with liquid cooling ofprocessors, such as adequately ensuring tightness, are still in noreasonable relation to the benefits.

In view of the ever increasing computing power in less and less space itcan be assumed that the cooling load and associated energy consumptionwill also increase.

OBJECT OF THE INVENTION

Therefore, an object of the invention is to reduce the energyrequirements of a conventional cooling system for computing systems.

DESCRIPTION OF THE INVENTION

The object of the invention is already achieved by a system for coolinga computing system, by a computing system, and by a method for cooling acomputing system according to any of the independent claims.

The invention relates to a system for cooling a computing system, whichcomprises a refrigeration machine. A refrigeration machine commonlyrefers to a device which is used to produce cold, i.e. a temperaturethat is lower than the ambient temperature.

The invention especially relates to compression-type refrigerationmachines, i.e. refrigeration machines having a mechanical compressor bymeans of which the coolant is liquefied and can subsequently evaporatein the cold section of the refrigeration machine, whereby it cools downand produces the cooling effect.

However, the invention also relates to any other types of refrigerationmachines, in particular sorption refrigeration machines such asadsorption or absorption refrigeration machines, in particularrefrigeration machines operating on the principle of absorptivedehumidification, also commonly referred to as a desiccant coolingsystem (DCS), refrigeration machines operating on the magnetocaloriceffect, refrigeration machines operating with Peltier elements,geothermal refrigeration machines, steam jet refrigeration machines,refrigeration machines operating on the Joule-Thomson effect, and/orrefrigeration machines operating on the principle of evaporativecooling.

According to the invention, the computing system comprises at least afirst and a second cooling circuit, wherein the first cooling circuit isoperable via a liquid and/or via heat conduction. That means, the firstcooling circuit is not an air-based cooling system. Rather, the coolingeffect is accomplished using a liquid such as water, or by heatconduction whereby the heat is directly discharged from theheat-generating components via components having a good thermalconductivity. Heat conduction also refers to the use of heat pipes whichremove the heat more quickly due to a condensation and evaporationprocess. Further, according to the invention, at least the secondcooling circuit which usually is an air-based cooling circuit, isconnected to a cold section of the refrigeration machine.

The invention in particular suggests to cool components which areoperated at high temperature, in particular the processor, using aliquid-based or heat conduction based cooling circuit. Due to the hightemperatures, in particular a temperature above 50° C., at which thesecomponents can be operated, it is often possible to discharge theproduced heat to the outside without the use of a refrigeration machine,or to further use it as useful heat for heating purposes and hot waterpreparation.

The processor cooling circuit in the sense of the invention may not onlyinclude the main processors of the computing system, rather theprocessor cooling circuit may also include additional processors andelectronic devices such as memory circuits, hard disks, chip sets, powercomponents of the power supply, which in turn are included in differentcomponents of the computing system such as in server racks,telecommunications equipment, power supplies, data storages, and othercomponents of the computing system.

Hence, the computing system in the sense of the invention not onlycomprises the servers but also other power supply components, especiallypower adaptors and emergency power supplies, communication modules, datastorages, etc.

The second cooling circuit which is typically configured as an air-basedcooling circuit and is connected to the cold section of a refrigerationmachine, now only needs to remove the energy which cannot be discharged(or is not discharged) through the first cooling circuit which isoperated at a much higher temperature. The second cooling circuittypically operates at a feed flow temperature which does notsubstantially exceed 20° C., in particular at a maximum of 20° C.Specifically, this cooling circuit may be configured as a closed systemto which the components of the computing system are connected. Since,now, the amount of heat to be dissipated over the comparativelyinefficiently operating refrigeration machine is low, the cooling energyrequired for the system can be reduced considerably.

The invention thus relates to a system for cooling a computing systemhaving a plurality of cooling circuits, in particular at least twocooling circuits, wherein by distributing the total thermal energy to bedischarged to a plurality of cooling circuits a distribution is effectedto different temperatures of these individual cooling circuits, whichpermits, based on the respective temperature of this thermal energy, tocool a fraction or several fractions of the total thermal energy to bedischarged in a particularly efficient manner, or to supply it for afurther use.

In one embodiment of the invention, a return flow of the first coolingcircuit can be connected with both a heat exchanger and the cold sectionof the refrigeration machine. For example, the heat exchanger may bemounted to the outside of a building. However, a heat exchanger in thesense of the invention also refers to a reuse of the cooling fluid, forexample for generating useful heat. Due to the fact that the firstcooling circuit, in particular the processor cooling circuit, can beconnected both to a heat exchanger, in particular an outside heatexchanger, and to the cold section of the refrigeration machine, it ispossible to selectively distribute the amount of heat which is to bedischarged through the refrigeration machine and which is to bedischarged through the heat exchanger, in particular via a directionalvalve. So in order to cool the first cooling circuit the refrigerationmachine has only to be used if, for example due to an elevated outsidetemperature, cooling via an externally arranged heat exchanger is nolonger possible. Thus, the energy-intensive use of the refrigerationmachine is reduced to a minimum, while the system enables to providereliable cooling even in case of very high outside temperatures.

In one embodiment of the invention, the cooling fluid may be passedthrough nearby heat exchangers which are connected to the printedcircuit boards and so cool the printed circuit boards and/or the devicesthermally coupled with the printed circuit board. Also, the coolingfluid may be passed through the printed circuit boards themselves.

One embodiment of the invention comprises at least three coolingcircuits, one cooling circuit thereof being operated by air and theother two cooling circuits being operated by means of a liquid or heatconduction, and at least one cooling circuit of the other coolingcircuits, i.e. the liquid-based cooling circuits, can be connected bothto an external heat exchanger and to a cold section of the refrigerationmachine. The so defined system effectively operates as a three-stagesystem. Specifically, it is intended to provide three cooling circuitswith different feed flow temperatures.

For example, the processors of the computing system may be cooled by afirst cooling circuit having the highest feed flow temperature. Thiscooling circuit usually does not required the support of a refrigerationmachine, rather it is possible, at least in temperate climates, toremove the heat to the outside via an external heat exchanger.Alternatively, it is possible to use the high temperature level forother purposes, for example to heat buildings, or to produce hot wateror electricity. It will be understood that it may yet be useful toconfigure the system in such a way that the fluid of this coolingcircuit may likewise be fed to the cold section of the refrigerationmachine in order to ensure reliable cooling even at extremely highoutside temperatures.

Another liquid-based cooling circuit is operated at a feed flowtemperature which is between the feed flow temperature of the abovementioned cooling circuit and the feed flow temperature of a further, inparticular air-based, cooling circuit. Another group of heat-generatingcomponents which are cooled using a lower feed flow temperature than thecomponents of the first cooling circuit can be connected to this coolingcircuit. These may be hard disks and storage devices, for example.

This second cooling circuit whenever possible uses an external heatexchanger so that the use of the refrigeration machine can be dispensedwith. So depending on the climate zone it is possible, at least in thewinter months, to operate even this other cooling circuit without usinga refrigeration machine. In case of elevated outside temperatures, onthe other hand, recourse is made to the refrigeration machine byselectively distributing the coolant.

Another cooling circuit is usually air-based and operates at a lowerfeed flow temperature than the two abovementioned cooling circuits. Thiscooling circuit for example cools the air in the racks or even the airin the room in which the computing system is installed. Since for thispurpose, generally, temperatures of 20° C. or below are needed, thisgenerally requires the use of a refrigeration machine. However, becauseof the heat discharge over the two other cooling circuits it is possibleto considerably reduce the use of the refrigeration machine. It will beappreciated that depending on the size and configuration of the system,more other cooling circuits may be provided at intermediate temperaturesin order to optimize the system so that as much heat as possible may bedischarged without using refrigeration machines.

Furthermore, as suggested according to another embodiment of theinvention, the system may comprise means for selectively distributingthe cooling fluid within the computing system.

In particular, it is suggested to distribute the cooling capacity withinthe computing system in function of the workload thereof. According toone embodiment of the invention, the system for cooling the computingsystem may be connected with the computing system itself, to optimizethe distribution of coolant. It is conceivable, for example, that atleast some individual servers of the computing system report, via aninterface, the respective work load and/or the respective temperature tocontrol electronics of the cooling system, so that the cooling system iscontrolled in function of the work load, in particular regarding thelocal distribution of different processing powers or waste heatgeneration within servers, racks, components of the computing center andwithin the computing center itself.

One advantage of such a control system is, inter alia, that additionalcooling capacity is already requested at a very early stage, namelyimmediately upon an increase of utilization of the computing system. Inthis way, for example in cooling systems including a cold storage, therequired capacity of thermal storages for storing cold may be reduced byhaving the refrigeration machine already switched on as soon as a needfor additional cooling energy is foreseeable due to the utilization ofthe computing system (and not only when the temperature in the computingsystem has already risen) and thus reducing the time to be bridged by acold storage between the demand of cooling energy and provision thereofby the refrigeration machine (the refrigeration machine usually requiresa few seconds or minutes from its activation to provide the coolingenergy). Smaller thermal buffers permit more compact configurations,which may be of advantage especially in case of cooling modulesintegrated in the computing system, e.g. in racks, or connected to theracks.

Furthermore, it is conceivable in case of an increase of computing powerto increase the amount of coolant supplied and/or to reduce thetemperature thereof. In particular it is also conceivable in case ofincreasing computing power to operate at least one coolant circuit at alower temperature.

Moreover, in contrast to simpler control systems which are controlledfor example based on the return flow temperature, it is possible in caseof a lower work load to operate the computing system at a significantlyreduced power without the risk that in case of a sudden increase of thework load overheating of individual components occurs due to the lowcooling capacity supplied.

A temperature monitoring program may be installed on the individualcomputers to control the cooling system, which runs in the backgroundand reports increasing cooling requirements to the controller of thecooling system. As an interface in the context of the invention analready existing LAN port may be used, for example.

Also conceivable is remote monitoring and/or control of the coolingsystem via a network, in particular based on the internet.

In one embodiment of the invention, both the first cooling circuit andthe hot section of the refrigeration machine each include a heatexchanger, which heat exchangers are thermally coupled via another heatexchanger, so that the waste heat from the two cooling circuits may bedischarged collectively. This embodiment of the invention is based onthe realization that the hot section of a refrigeration machine, inparticular a compression-type refrigeration machine, through whichgenerally the heat extracted from the system is discharged to theoutside, and a processor cooling circuit may be operated at similar feedflow temperatures. If now the two cooling circuits are coupled via heatexchangers, the generated heat may be discharged to the outside using asingle heat exchanger. An advantage thereof is that only one externalport has to be provided. This is particularly advantageous inconjunction with the modular configuration described herein, or with theembodiment in which the refrigeration machine is integrated in theserver or directly connected to the server.

In one embodiment of the invention, the system comprises at leastredundantly configured pumps for distributing the cooling fluid and/or aredundantly configured refrigeration machine. At least in larger serverfarms, even in case of a failure of individual components of the coolingsystem permanent continued supply of the cooling fluid has to be ensuredfor a long time, for which purpose buffering storages are generally notsufficient.

For emergency cooling, an additional conventional refrigerationcompressor or a supply of cold tap water into the system may beprovided, for example.

Furthermore, the cooling circuits themselves may be configuredredundantly, so that for example in case of a loss of coolant in acooling circuit the heat may be removed via a cooling circuit redundantthereto.

In one embodiment of the invention, the system may be integrated into anexisting air conditioning system of a building and/or into a hot watersupply system and/or into an electricity supply system. For example, itis conceivable that the process heat which results from a refrigerationmachine is used at least partly to heat the building and/or to providehot water. It is also conceivable to use the process heat to generateelectricity, for example using Peltier elements. The term process heatrefers to any kind of energy removed from the cooling system, alsoreferred to as recooling.

However, it is also conceivable, as suggested according to anotherembodiment of the invention, to use a refrigeration machine which isoperated using heat as driving energy. This is in particular the casewith sorption refrigeration machines. In such an embodiment of theinvention it is possible to connect the first cooling circuit whichoperates at a higher feed flow temperature to the hot section of therefrigeration machine so as to provide driving energy. The secondcooling circuit may then be connected to the cold section of therefrigeration machine to cool the air in the servers, for example.Especially advantageously, the fluid discharged from the hot section ofthe refrigeration machine is passed through an external heat exchanger.This is because this fluid usually still has a sufficiently hightemperature so that heat can be discharged externally to the outsidewithout the use of refrigeration machines (depending on the particular,for example climate-related, outside temperatures).

In a preferred embodiment of the invention, the system has a modularconfiguration and comprises at least one cooling module in which atleast the refrigeration machine and an electronic controller arearranged. It is in particular suggested to provide a module whichcomprises a housing with ports, and to which, in addition to a powersupply and optionally the connection of the computing system via aninterface, the feed and return conduits of the cooling circuit of thecomputing system can be connected. Furthermore, the module preferablycomprises ports for an external heat exchanger through which processheat from the refrigeration machine is discharged.

The controller of the system for cooling a computing system is alsointegrated in the module.

The modules are preferably sized according to the system dimensions ofcomponents of the computing center, e.g. as a 19″ system for rackcomponents.

Ports for electric power supply, for communications and/or for coolingconduits are preferably configured so as to be automatically connectedwhen the module is inserted. In this way, a faster installation isrealized for maintenance and replacement purposes.

Moreover, in a preferred embodiment of the invention, the module has atleast one independent emergency power supply which at least ensures theoperation of the pumps which supply the cooling fluid to the computingsystem, even in the event of a power outage. It is conceivable toadditionally connect at least one control electronics of the coolingsystem to the emergency power supply. For simpler control is alsopossible to drive the pumps such that they continue to run in case thecontrol electronics is switched off.

Alternatively, the emergency power supply of the cooling system may beensured by an emergency power supply of the computing system, inparticular by an uninterruptible power supply.

Computing systems generally have an uninterruptible power supply. Suchuninterruptible power supplies of computing systems are usually alsocooled. Therefore, it is intended to use the cooling system also for theuninterruptible power supply. An uninterruptible power supply generallycomprises at least accumulators which can bridge momentary interruptionsof the mains voltage. The uninterruptible power supply usually starts upwithin a few milliseconds, so that even short term voltage disturbancesare compensated for.

A computing system usually also has telecommunications devices, such asmodules for connection to a telecommunications network. It will beappreciated that the cooling system according to the invention, ifnecessary, also ensures cooling of these telecommunications modules.

In another embodiment of the invention, a liquid of the second coolingcircuit, after having passed through a cold section of the refrigerationmachine, may be fed through a heat exchanger to cool the air prevailingin the computing system. That is, as already described above, the secondcooling circuit is air-based, and the air is cooled down by a heatexchanger which is for example integrated in a rack of the computingsystem.

In this embodiment of the invention, the liquid after having passedthrough the heat exchanger is fed to the first cooling circuit.Therefore, this is an embodiment in which the two cooling circuits areconnected in series, so that the cooling fluid first supplies cold tothe second cooling circuit which is operated at a low feed flowtemperature, and is then fed to the first cooling circuit, in particularthe processor cooling circuit, at a higher temperature.

In one embodiment of the invention, the refrigeration machine isintegrated in a rack or in a server. This particularly permitsrefrigeration machines to be accommodated in the system in decentralizedmanner. Also, this may permit a server to cool itself, for example. Inthis case each cooling circuit may be optimized to the specificindividual device. A port for a cooling circuit in the sense of theinvention refers to any type of interface through which heat energy canbe transferred.

In one embodiment of the invention, refrigeration machines are providedintegrated in or immediately adjacent to a server, the refrigerationmachines being configured as a module.

Preferably, each module comprises heat exchangers, controllers, pumps,interfaces, and the refrigeration machine itself. However, providingjust the refrigeration machine as a module is also conceivable.

It is also possible, as suggested according to another embodiment of theinvention, that the refrigeration machine (preferably implemented as amodule) is arranged immediately adjacent to the server or rack. Forexample, the refrigeration machine may be disposed above or below aserver or rack. So no additional footprint is required. It is alsopossible that the cooling module is arranged laterally, also, onerefrigeration module may supply several components such as racks withcooling energy.

As is known, heat exchangers and fans for generating an internal aircirculation for cooling a rack, for example, such as those of a rackcooling system, may be arranged both within or adjacent to a rack, forexample. So in another embodiment of the cooling module, an arrangementof the cooling module in such a unit for internally cooling for examplea rack is possible.

In one embodiment of the invention, the refrigeration machine isintegrated in a server, in particular a blade server.

According to one embodiment, the refrigeration machine is configured asa module that is insertable into a server, in particular as a plug-inmodule. This embodiment of the invention may be used for conventionalblade servers, for example.

Integration into the server or the computing system, or an arrangementdirectly adjacent thereto allows for short cable lengths and transferpaths for the coolant (liquid, heat conduction, air), thereby reducingthermal losses of the cold transfer, furthermore reducing the energyrequired for the cold transfer (e.g. the pump power), and henceincreasing efficiency. Furthermore, integration or adjacent arrangementof the cooling modules allows a modular configuration of the computingcenter with respect to the cooling system; the components (e.g. racks)each comprise a separate cooling system tailored to the component. Thus,the computing center can be extended without the need to extend acentral cooling system or to expand the cooling capacity thereof (exceptfor the discharge of process heat). Furthermore, a computing center isconceivable that does not require a central cooling system (except forthe discharge of process heat). Another advantage of integrated oradjacent cooling modules, depending on the embodiment, is a reduction ofexternal ports for the cooling circuits when several cooling circuitsare already combined in the cooling modules. So, for example, only onefluid port is needed as an external port to discharge process heat.Otherwise, all components can be integrated in the server or the rack.

A system for cooling a computing system may be configured such thatnon-adjacent and non-integrated cooling modules or refrigerationmachines and adjacent or integrated refrigeration machines or coolingmodules are used in an optimum combination in terms of investment costsand operating costs.

In one embodiment of the invention, the system for cooling a computingsystem comprises a system for detecting a loss of coolant and forinitiating an emergency shutdown in a loss of coolant event, which mayalso be configured as a module.

In particular, the means for emergency shutdown are configured as apower supply interrupter.

For example, in a liquid-based cooling system which is preferablyoperated at a positive pressure for pressure detecting purposes, it isconceivable to centrally detect based on the pressure if a fluid leakexists.

Then, in the event of a drop of pressure, for example the entirecomputing system or portions of the computing system and/or the pumpsfor circulating the coolant may be switched off, so that the componentsare disconnected from power. This ensures that at worst components aredamaged which come directly into contact with the cooling water, andthat other damage to components due to the electric conductivity of thecooling water is avoided by disconnecting the power supply of thecomponents.

Furthermore, it is conceivable that the emergency shutdown comprises apump which in the event a loss of fluid is detected generates a negativepressure in the coolant system. For example, the pump may pump out theliquid into a designated reservoir or into drains. Due to the resultingnegative pressure no or only little additional water will leak, so thatthe damage in the system remains localized.

In another embodiment of the invention, means for emergency shutdown areintegrated in a rack of the computing system.

For example, each rack may comprise means for detecting a loss ofcoolant, in particular a humidity sensor. In case of a liquid leakage,the power supply of the rack is disconnected. It is likewise possible toprovide the rack with automatically closing valves, so that it isseparated from the coolant circuit. An advantage of this embodiment ofthe invention is that in this way not the entire computing system fails,and at the same time leakage of larger amounts of fluid from a rack isprevented.

Furthermore, the module for detecting a loss of coolant may be acomponent of a cooling module.

In one embodiment, the invention provides for a system for cooling acomputing system that comprises a plurality of cooling circuits, whereinone cooling circuit is coolable without using the refrigeration machineand another cooling circuit is coolable using the refrigeration machine.In particular, it is suggested to discharge the waste heat of a firstcooling circuit having a higher feed flow temperature and higher returntemperature without the use of a refrigeration machine by using theoutside air for recooling, or by using the heat as useful heat, forexample for heating purposes and for hot water supply.

Alternatively, or in combination therewith, at least two coolingcircuits are coupled thermally and so are combined to form one coolingcircuit.

In particular, it is suggested to connect at least two cooling circuitswith a lower and a higher feed flow temperature, respectively, inseries. So, for example, the return flow of a rack cooling circuit maybe used to cool power components and processors.

In one embodiment of the invention, process heat is dischargeablethrough the combined cooling circuit. In particular, the return flow ofthe last cooling circuit which has the highest temperature is suppliedto a heat exchanger.

In one embodiment of the invention, the system for cooling a computingsystem comprises a plurality of cooling circuits, wherein at least inone cooling circuit a bypass is provided, by which the volume flow inthe module to be cooled and connected to the cooling circuit may beincreased by a partial recirculation of the coolant without increasingthe total volume flow of the coolant in the cooling circuit. So it ispossible to keep the total volume flow substantially constant, and todirect a portion of the volume flow to detour components to be cooled,via a bypass. If now additional cooling is required, the flow rate inthe bypass may be reduced, whereby the flow rate along the components tobe cooled increases.

However, vice versa it is likewise possible to reduce the volume flow inthe module connected to the cooling circuit without reducing the totalvolume flow in the cooling circuit.

In one embodiment of the invention, a liquid is used as the coolantwhich has an electrical conductivity of less than 10*10⁻⁶ S/m.Specifically, pure water or a water-glycol mixture may be used. In thisway, electrical damage to the components of the computing system and therisk of electric shock to operating personnel are reduced.

In one embodiment of the invention, components of the refrigerationmachine, in particular a compressor, may be cooled using at least one ofthe cooling circuits. Thus, the refrigeration machine is integrated insimple manner into the cooling of the system and is in particular cooledby a liquid.

In particular, by connecting the compressor or the motor of thecompressor to one of the liquid-based cooling circuits, the waste heatof the compressor or of the compressor motor (motor heat) may be furtherused for example as thermal energy (for example for building heating orfor generating electric energy). Moreover, this may avoid the need forgenerating the cooling power to cool the compressor of the refrigerationmachine by the refrigeration machine itself (or by another refrigerationmachine), by removing the motor heat via another cooling circuit whichcan be cooled directly in the recooling without any other refrigerationmachine, for example because of its high temperature. In this way, theenergy required to cool the computing center is reduced.

In another preferred embodiment of the invention, a refrigerationmachine is used which comprises a compressor that has a soft startcircuit.

A soft start circuit reduces the inrush current and thus reduces thetorque of the motor in the start-up phase. In addition to a softerstart, the service life of the motor may be significantly increased inthis way.

The invention provides for a substantially thermally neutral computingsystem which merely releases a heating power of less than 20%,preferably less than 10% of the power consumption of the computingsystem as thermal energy into a room in which the computing system isinstalled. Therefore, in many cases cooling of the room by anenergy-consuming refrigeration machine can be dispensed with.

Thus, the computing system may possibly also be installed in officeareas, etc.

For reducing the heat transfer to the environment, a housing of thecomputing system may be insulated, in particular the housing walls mayhave a heat transfer coefficient of k<3 W/m²K, preferably k<1 W/m²K.

For this purpose, the housing walls may comprise a thermally insulatingmaterial, such as hard foam. It is also conceivable to apply insulatingmaterial to the inner and/or outer surface of the housing walls.

Furthermore, the housing walls of the computing system may be coolableto approximately ambient temperature using fluid lines which areconnected to a cooling circuit. To this end, the walls may be of adouble-walled construction or may include cooling coils. By cooling thewalls, unwanted release of heat into the environment can be prevented,even with a temperature in the housing above room temperature.

The invention further relates to a computing system and in particular toone embedded in a system as described above for cooling a computingsystem. As far as details of the computing system and cooling systemthereof have been described above, reference can be made to thecorresponding features concerning the computing system, without thecomputing system necessarily being a part of the system described above.

The computing system comprises a housing in which the components of thecomputing system, in particular processors, memory, hard discs, etc. arearranged.

According to the invention, the computing system comprises at least afirst and a second cooling circuit, wherein the first cooling circuitpermits to cool processors and power components of the computing systemusing a liquid and/or by heat conduction, and wherein the second coolingcircuit comprises a heat exchanger arranged in the housing.

By the heat exchanger which in particular can be cooled by a liquid, theinside of the housing is cooled by a cooling circuit, and in this waythermal energy is discharged, which is not removed through the firstcooling circuit. The heat exchanger may for example comprise a coolingcoil arranged in the rack, or channels in the housing.

Preferably, the computing system includes fluid ports for both the firstand the second cooling circuit.

While due to the high temperature the major part of the thermal energymay be discharged through the first cooling circuit by free cooling, itis also possible, other than with the system for cooling a computingsystem described above, to dispense with the use of a refrigerationmachine for the remaining thermal energy discharged through the secondcooling circuit, and to also operate this cooling circuit via freecooling.

In this way, the computing system may be configured to be thermallyneutral.

The housing is preferably formed as a rack.

The invention further relates to a cooling module, in particular for asystem for cooling a computing system as described above.

The cooling module comprises a port for a first cooling circuit, inparticular a cooling circuit which permits to cool processors and powercomponents of a computing system using a liquid. Moreover, the coolingmodule comprises another port for a further cooling circuit. Thisfurther cooling circuit permits to cool for example housings or serversof a computing system, at a lower temperature. Furthermore, the coolingmodule comprises a port for discharging process heat. Via this portrecooling is accomplished such that thermal energy is removed from thecooling system.

In a preferred embodiment of the invention, the cooling module comprisesa refrigeration machine. The refrigeration machine is in particularintended to provide a sufficiently low temperature for the secondcooling circuit which is operated with a lower feed flow temperature.

In one embodiment of the invention, the cooling module is configured asa plug-in module for a server, in particular a blade server.

To this end, the cooling module includes mechanical means to be insertedinto a slot. The cooling module has a standard size which occupies oneor more slots of a server.

The invention further relates to a housing of a computing system, whichis in particular configured as a rack. The housing includes a heatexchanger arranged in the housing, and a fluid port connected to theheat exchanger. Also, the housing walls may be formed as a heatexchanger.

The heat exchanger permits to cool the interior of the housing.

Furthermore, the housing comprises another fluid port to which modules,in particular plug-in modules or power components, may be connected.

The invention further relates to a computing module, which is configuredas a plug-in module for a rack. A computing module may compriseprocessors, for example, but also hard disks, telecommunicationselectronics, etc.

According to the invention, the rack comprises a fluid port throughwhich processors and power components of the computing module may besupplied with a cooling fluid.

The computing module may comprise a further fluid port for supplyingcooling fluid which in particular cools the housing of the computingmodule, for example using an integrated heat exchanger. However, it isalso conceivable to accomplish cooling of the housing merely based onair, so that the housing in which the computing module is disposed iscooled down by a heat exchanger arranged in the housing.

The invention further relates to a module for detecting a leak, inparticular for a system for cooling a computing system as describedabove. The module comprises means for detecting a leak in the coolingsystem, a controller, and means for shutting down a computing system, atleast partially.

Preferably, the module for detecting a leak is adapted to determine thelocation or size of the leak based on measured parameters such as thepressure in the fluid system, moisture sensors, etc., and thenselectively shuts down the computing system or performs an emergencyshutdown by interrupting the power supply, in function of the locationand severity.

The module for detecting a leak may be incorporated in another componentsuch as the cooling module described above. Likewise, it is conceivablefor the module itself to be configured as a plug-in module for a server.

The invention further relates to a method for cooling a computingsystem, in particular using a system for cooling a computing system asdescribed above.

The computing system comprises at least a first and a second coolingcircuit, wherein the first cooling circuit is operated at a highertemperature than the second cooling circuit and by means of a liquidand/or by heat conduction. Specifically, the feed flow temperatures ofthe two cooling circuits differ by at least 20° C., preferably by atleast 30° C.

Furthermore, at least the second cooling circuit is operated through acold section of a refrigeration machine.

The invention permits to reduce the cooling power generated by therefrigeration machine to a minimum, since the first cooling circuitwhich for example is configured as a processor cooling circuit asdefined above is operated at such a high feed flow temperature that theheat can be removed without the use of a refrigeration machine, at leastfor the majority of the time.

In one embodiment of the invention, the return flow of the first coolingcircuit is temporarily connected both to a heat exchanger and to thecold section of the refrigeration machine, in particular by means of adirectional valve.

Therefore, waste heat from the first cooling circuit is only fed to therefrigeration machine if an external discharge thereof, for example viaa heat exchanger, is not possible, for example due to high ambienttemperatures.

The first cooling circuit preferably provides for cooling processorsand/or power components of the computing system, whereas the secondcooling circuit preferably cools the racks of the computing systemand/or the room in which the latter is arranged.

A heat exchanger also refers to providing the heat of the hot section ofthe refrigeration machine and/or the heat of the first cooling circuitfor useful heat in particular for room heating and/or water preparation.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a first embodiment of a system 1 forcooling a computing system.

Shown is a server with two cooling circuits.

The first cooling circuit is a liquid-based cooling circuit andcomprises a feed flow line 2 and a return flow line 3, through whichliquid-cooled components may be cooled, such as processors and otherpower components.

Furthermore, the system 1 for cooling a computing system comprises asecond cooling circuit in form of an air cooling, comprising a fluidinlet 4, and an outlet 5. This second cooling circuit is coupled with arefrigeration machine (not shown).

The second cooling circuit serves to cool components 7 which are notconnected to the liquid-based cooling circuit.

The first cooling circuit is coupled to a heat exchanger, via feed flow2 and return flow 3, and the heat generated thereby may be used asuseful heat for the building. The first cooling circuit may be operatedat a higher temperature, for example the target temperature may be 50°C. at the feed flow and 60° C. at the return flow. Due to the highpossible feed flow temperature, a refrigeration machine is notnecessarily required for cooling.

The second cooling circuit comprising the air cooling, by contrast, iscoupled with a refrigeration machine (not shown), since it has to beoperated with a lower temperature, for example the temperature is notmore than 20° C. at the inlet and 35° C. at the outlet.

However, since much of the energy to be discharged as heat can beremoved via the first liquid-based cooling circuit, there aresignificant energy savings resulting in the system for cooling acomputing system.

The saved energy is calculated from the amount of energy discharged viathe first cooling circuit divided by the efficiency, or coefficient ofperformance (COP), of the refrigeration machine.

Since refrigeration machines usually work with poor efficiency, energysavings are considerable.

Referring to FIG. 2, the principle of a refrigeration machine will beexplained schematically. The refrigeration machine in this embodiment isa compression-type refrigeration machine.

Refrigeration machine 8 comprises a coolant circuit 13 which may beconsidered as the refrigeration machine's internal coolant circuit. Thecoolant in evaporator 9 expands, thereby becoming gaseous and causing atemperature decrease. Evaporator 9 forms the cold section of therefrigeration machine. Via a compressor 10, the coolant is fed throughthe cooling circuit 13 to a condenser. Through an increase of pressurethe coolant liquefies and can release waste heat at the condenser toextract energy from the system. Condenser 11 forms the hot section ofthe refrigeration machine 8. Via expansion valve 12, the coolant isagain fed to the evaporator, and thus a closed circuit is formed.

FIG. 2 a schematically illustrates a refrigeration machine, in which theinternal coolant circuit 13 is connected, via an internal heat exchanger59, to coolant ports outside the refrigeration machine.

FIGS. 2 and 2 a thus illustrate the possibility of configuring a coolingcircuit according to the invention such that it includes, instead of acooling liquid (for example water), the coolant of the refrigerationmachine, wherein cooling is accomplished directly through the evaporatorof the refrigeration machine. In this manner, the size of therefrigeration machine can be reduced, which may be important inparticular for refrigeration machines integrated in servers, forexample.

Referring to FIG. 3, the thermal connection of a refrigeration machinewill be explained. Refrigeration machine 8 comprises a cold section 16having an inlet 14 and an outlet 15. Cold section 16 for example coolsthe second cooling circuit of a system for cooling a computing system.

Hot section 19, likewise, comprises an inlet 17 and an outlet 18. Thehot section, for example, may have a feed flow temperature of 50° C.,whereas the return flow temperature of the cold section is 15° C., forexample.

FIG. 4 schematically illustrates an exemplary embodiment of a system 1for cooling a computing system.

The system 1 for cooling a computing system comprises a first coolingcircuit 21.

The first cooling circuit is a liquid-based cooling circuit which servesto cool processors and power components arranged in rack 20.

Through the first cooling circuit 21, heat is fed to the environment viaheat exchanger 23. It will be understood that this heat may be used asuseful heat, or to generate electric energy.

Furthermore, the system 1 for cooling a computing system comprises asecond cooling circuit 22. Second cooling circuit 22 comprises a heatexchanger 24 built into the rack 20 or connected to the rack 20, whichserves to cool the air in rack 20 and in a rack-internal air circuit.Cooling circuit 22 is connected to a refrigeration machine 8.

The feed flow temperature of cooling circuit 22 is substantially lowerthan that of cooling circuit 21. Therefore, the use of refrigerationmachine 8 which is in particular configured as a compression-typerefrigeration machine is necessary, unless free cooling can be used, asmentioned above.

Waste heat, also referred to as process heat, is discharged to theoutside by heat exchanger 25 through the hot section of refrigerationmachine 8.

FIG. 5 shows another embodiment of a system 1 for cooling a computingsystem. Here too, the system comprises a first cooling circuit 21, whichis water-based.

In contrast to the exemplary embodiment illustrated in FIG. 4, the airdirected through modules 26 of the server is cooled by a heat exchanger24 connected to the second cooling circuit 22 after leaving thecomputing system. However, it is also possible to have the air cooledbefore entering the computing system instead of after leaving thecomputing system (not shown).

FIG. 6 shows another embodiment, in which in contrast to the aboveembodiments the second heat exchanger 24 connected to the coolingcircuit is mounted apart from the rack of the computing system. Using afan 27 the air may be set in motion, and the second cooling circuit maybe implemented with a lower feed flow temperature, for example using theair-conditioning of the room in which the servers are installed.

FIG. 7 shows another embodiment of a system 1 for cooling a computingsystem, which is based on the principle of the embodiment illustrated inFIG. 4. Here, instead of external heat exchangers, both therefrigeration machine is provided with a port 28 and the first coolingcircuit is provided with a port 29, through which the heat may beremoved and provided as useful heat, for example for building heating,hot water supply, or for generating electric energy.

FIG. 8 shows an exemplary embodiment of a system 1 for cooling acomputing system, in which a refrigeration machine can be dispensedwith.

A first cooling circuit 21 provides liquid-based cooling, which coolsthe processors and power components of the computing system 30.

Via port 29 the heat may be provided as useful heat (for example forbuilding heating, hot water supply, or for generating electric energy),or may be discharged to the outside.

The second cooling circuit 22 comprises a heat exchanger 24 preferablyarranged in the rack of computing system 30, by which the air in therack is cooled. Due to the small amount of heat to be discharged, tapwater may be used as a cooling medium, for example. It will beunderstood that it is also conceivable, for example, to preheat the tapwater for hot water supply (for example by heat exchangers—not shown),so that the energy extracted from the second cooling circuit may beused, which only results in a return flow temperature of for examplebelow 30° C.

FIG. 9 shows another embodiment of the invention, wherein the secondcooling circuit 22 is connected to the first cooling circuit 21.

In this embodiment, the cooling fluid cooled by refrigeration machine 8is first supplied to heat exchanger 24 which cools the air in the rack.

The so already heated coolant fluid is then passed into the firstcooling circuit 21 and cools the processors and power components.

In this manner, the cooling circuits are connected in series, and thecooling liquid, for example provided by a refrigeration machine, firstpasses through the cooling circuit with the lower temperature level andthen through the cooling circuit with the higher temperature level. Itwill be appreciated that more than two cooling circuits can be connectedin series in this way, for example the cooling circuits 21, 22, and 38of server 37 shown in FIG. 13.

With reference to the drawings of FIGS. 10 to 12, different ways ofdischarging the waste heat will be explained.

In the exemplary embodiment of a system 1 for cooling a computing systemshown in FIG. 10, the first cooling circuit 21 for cooling theprocessors and power components is connected to an external heatexchanger 23. The hot section of refrigeration machine 8 is connected toanother, separate heat exchanger 25 through which process heat isdischarged.

FIG. 11 shows another exemplary embodiment, in which the hot section ofrefrigeration machine 8 is connected to the first cooling circuit 21.This is possible since for the processors it suffice to provide acooling fluid at a temperature of 50° C., for example.

The fluid extracted from the return flow of the first cooling circuit 21is first passed via a heat exchanger 25 and then fed into the returnflow of the warm section of refrigeration machine 8.

This embodiment may also be referred to as a sequential cooling circuit.

FIG. 12 shows another exemplary embodiment of a system for cooling acomputing system.

In this embodiment, an intermediate heat exchanger 31 is provided.Coupled to heat exchanger 31 is both the first cooling circuit 21 forcooling the processor as well as a cooling circuit 32 which forms thecooling circuit of the hot section of the refrigeration machine. Heatexchanger 31 thermally combines these cooling circuits and couples themto heat exchanger 25 arranged outside.

An advantage of this embodiment of the invention is that thus only twoports are required for connecting an external heat exchanger 25. Becauseof a maximum temperature difference of 20° C., preferably 10° C., in thefirst cooling circuit 21 and in cooling circuit 32 of the refrigerationmachine this is possible in a particularly simple manner.

With reference to FIGS. 13 to 15, a system 1 for cooling a computingsystem with three cooling circuits will be described in detail by way ofa schematically illustrated exemplary embodiment.

Referring to FIG. 13, the essential components of the system 1 forcooling a computing system are described.

The system 1 for cooling a computing system comprises a first group ofheat generating components 34 which are connected to a first coolingcircuit 21 which is liquid-based.

A second group of heat generating components 35 which is likewisearranged in server 37 is also equipped with a liquid-based coolingcircuit. This additional cooling circuit will be referred to as a thirdcooling circuit 38 below.

A third group of heat generating components 36 is formed by heatgenerating components which are not connected to a liquid-based coolingcircuit.

These components 36 are cooled through air cooling by a second coolingcircuit 22 which comprises a heat exchanger arranged in the rack.

Furthermore, a refrigeration machine 8 is provided having a cold section16 by which at least the second cooling circuit 22 is cooled. The hotsection of refrigeration machine 8 is connected to an external heatexchanger.

Moreover, there is yet another external heat exchanger 23 provided,through which waste heat can be removed to the outside.

Now, the sense of this system is that three cooling circuits areprovided that work with different feed flow temperatures. The air-cooledcomponents of the third group of heat generating components 36 requirethe lowest feed flow temperature. The processors and power componentsassigned to the first group of heat generating components 34 are cooledwith the highest feed flow temperature, in particular with a feed flowtemperature of about 50° C.

Therefore, it is usually possible to largely or entirely dispense withthe use of a refrigeration machine, at least for the first group of heatgenerating components 34, and to cool them through external heatexchanger 23.

FIG. 13 illustrates a configuration in which the use of a refrigerationmachine is entirely dispensed with in the first group of heat generatingcomponents 34.

The second group of heat generating components 35 is cooled with a feedflow temperature which is between that of the first cooling circuit 21and that of the second cooling circuit 22.

Using valves 33, the cooling fluid of the third cooling circuit 38 maynow be selectively distributed to the heat exchanger 23 and the coldsection 16 of refrigeration machine 8.

Depending on the cooling power required and the current outsidetemperature, it is now possible to only have recourse to therefrigeration machine 8 for cooling the third cooling circuit 38 ifnecessary, for example due to high outside temperatures.

It will be appreciated that, in similar manner, the first coolingcircuit may be distributed selectively to heat exchanger 23 and to thecold section of refrigeration machine 8 (not illustrated), in functionof the required cooling power and the existing outside temperature.

Thus, FIG. 13 also illustrates that by means of valves and pumps (notshown) at least two cooling circuits may be selectively distributed toheat exchanger 23 and the cold section of refrigeration machine 8.

FIG. 14 shows the system 1 for cooling a computing system as illustratedin FIG. 13 in an operational state with an outside temperature below 30°C., for example below 30° C. and above 10° C. The respectivetemperatures of the feed and return flows are shown by way of example.

It can be seen that both the first cooling circuit 21 and the thirdcooling circuit 38 are connected such, by means of the valves, thatthese cooling circuits are connected to heat exchanger 23.

Therefore, only the second cooling circuit 22 has to be supplied throughthe refrigeration machine 8.

FIG. 15 shows an operational state of the system 1 for cooling acomputing system with an outside temperature of above 30° C., forexample above 30° C. and below 50° C. In this operational state, now,only the first cooling circuit 21 is connected to heat exchanger 23.Since the outside temperature no longer suffice to bring the fluid ofthe third cooling circuit 38 to a sufficiently low temperature, nowcooling circuit 38 is also connected to the cold section of therefrigeration machine. Thus, the refrigeration machine cools the thirdcooling circuit 38 and the second cooling circuit 22.

With reference to FIG. 16, the effect of the exemplary embodimentdescribed above for cooling a computing system will be explained in moredetail.

On top of FIG. 16, a curve is plotted which represents the temperaturein function of time. The time is represented on the X-axis, and thetemperature is represented on the Y-axis.

This could be both a temperature profile of a day as well as atemperature profile of the average temperature in a year.

Below the temperature graph, it is indicated when the refrigerationmachine has to be used. Periods in which the refrigeration machine hasto be used are marked by vertical lines, while periods during whichcooling may be accomplished through an external heat exchanger areindicated by oblique lines.

It can be seen that the first cooling circuit may be operated withoutusing the refrigeration machine for the entire time.

In contrast, the second cooling circuit, i.e. the cooling circuit of thethree cooling circuits which is operated with the lowest feed flowtemperature, however, has to be operated using the refrigeration machinefor a considerable period of time; only at night for example, and/oronly in the winter the use of the refrigeration machine may be dispensedwith.

The additional third cooling circuit with a feed flow temperaturebetween the feed flow temperatures of the first and second coolingcircuits further improves the efficiency of the system. This coolingcircuit needs to be operated through the refrigeration machine only at atemperature above 30° C.

FIG. 13 a shows, by way of example, a system for cooling a computingsystem. Server 37 and the three cooling circuits 21, 22, and 38 for thecomponents 34, 36, and 35 of server 37 have been described inconjunction with FIG. 13.

However, in contrast to FIG. 13, FIG. 13 a shows a configuration whichincludes free cooling, i.e. cooling without the use of a refrigerationmachine, which is illustrated and will now be described schematically byway of example based on the specified temperatures.

In this example, the three cooling circuits of the server are connectedin series, first cooling circuit 22 with a feed temperature of 15° C.and an outlet temperature of 20° C. This cooling circuit 22 is connectedto cooling circuit 38, with a feed temperature of 20° C. and an outlettemperature of 40° C. This cooling circuit 38 is in turn connected tocooling circuit 21, with a feed temperature of 40° C. and an outlettemperature of 60° C. Thus, the connection in series of these threecircuits as a whole results in a feed temperature of 15° C. (inlet ofcircuit 22), and an outlet temperature of 60° C. (outlet of circuit 21).Heat exchanger 25, in this example, provides an outlet temperature ofthe cooling fluid of 20° C. This cooling fluid is passed to a heatexchanger 56 for free cooling and cools the outlet temperature of thecooling fluid of cooling circuit 21 from 60° C. to 60° C.-ΔT, before thelatter is passed to the inlet of the cold section 16 of refrigerationmachine 8. Thus, the cooling power that has to be provided byrefrigeration machine 8 is reduced.

FIG. 17 shows an embodiment of the invention in which a refrigerationmachine 8, in particular a compression-type refrigeration machine, isbuilt into a rack 20 or arranged immediately adjacent to the rack 20(not shown). Refrigeration machine 8 is connected to a heat exchanger 24which forms the second cooling circuit for cooling the air prevailing inthe rack.

Process heat is discharged through the hot section of refrigerationmachine 8 and by heat exchanger 25.

Processors and power components are connected with a first coolingcircuit 21, and the heat therefrom is discharged to the outside throughheat exchanger 23.

FIG. 18 shows another exemplary embodiment in which again therefrigeration machine 8 is arranged in or on the rack.

Here, recourse is made to the sequential cooling described above, inwhich the return flow of the hot section of refrigeration machine 8 iscoupled to the first cooling circuit 21.

That means, the cooling fluid is first passed from the return flow ofthe hot section of refrigeration machine 8 via the processors and powercomponents.

Then, energy is extracted from the system using an external heatexchanger 25, and the cooling fluid is returned to the hot section ofrefrigeration machine 8.

FIG. 19 shows an overview of the components of a cooling module.

In particular, the cooling system is configured modularly to provide fora simple adaptation to the racks or other components of the computingcenter.

The possible components of a cooling module are shown in theorganization chart illustrated in FIG. 19. A cooling module may comprisea subset of the illustrated components. The components may be configuredas a cooling module, or non-modularly.

Especially the refrigeration machine is not forcibly a part of thecooling module, it may be arranged outside the cooling modules or onlyin one cooling module serving a plurality of racks, the lattercomprising another or each comprising another cooling module includingthe other components.

The cooling system is in particular configured modularly in order toprovide for a simple adaptation to the racks or other components of thecomputing center.

It is also possible that a cooling module comprises a subset of thecomponents shown. The components may be configured as a cooling module,or non-modularly. Therefore, it will be understood that the system mayconsist, as far as technically feasible, of any combination of thefollowing components.

Specifically, the individual components are defined as follows:

-   -   Refrigeration machine: Comprises a compression refrigeration        machine, or a sorption refrigeration machine, or a refrigeration        machine based on the magnetocaloric effect or on Peltier        elements. In order to achieve a high number of switching cycles        (a high number of switching cycles reduces the size of a cold        storage employed depending on the configuration of the cooling        module) without reducing the service life of the motors employed        in function of the type of refrigeration machine used, a soft        start circuit may be used for the compression refrigeration        machine. Furthermore, an electronic speed control may be used,        which permits analog control of the number of revolutions of the        compressor motor and thus of the amount of cooling energy        provided via this electronic speed control, instead of a digital        on-off control of the compressor motor, whereby the amount of        cooling energy provided is determined by the ratio of on-off        cycles.    -   Controller: Comprises hardware and software. The controller        serves to control all components of the cooling module.        Furthermore, the controller serves to (or may serve to) control        the temperatures of the cooling circuits, for example, or to        control the amount of cooling energy provided by the compressor,        or to control the amount of cooling energy transferred in the        individual cooling circuits. The amount of cooling energy        provided in the individual cooling circuits may for example be        controlled based on the temperature of the cooling fluid (with        the same volume flow, for example, more cooling energy is        transferred when lowering the outlet temperature of the cold        section of the refrigeration machine), or based on the volume        flow (with the same inlet and outlet temperatures of the cold        section of the refrigeration machine, more cooling energy is        transferred when increasing the volume flow of the cooling        fluid).    -   Cold storage, reservoir: The cold storage is necessary,        depending on the embodiment, in order to bridge the time        constant between turning on the compressor and the provision of        cooling energy, and in particular in order to reduce temperature        variations in the cooling circuit. Moreover, the cold storage        has an influence on the number of switching cycles during        operation if the cooling rate is controlled through on-off        cycles of the compressor, and therefore on the service life of        the refrigeration machine. The cold storage is required only        once per refrigeration machine. The cold storage may be        implemented as a sorption cold storage or as a latent cold        storage based on phase change materials, which is connected with        the cooling fluid via heat exchangers (not shown). Reservoirs        are necessary for filling the cooling circuits with liquid.    -   Interfaces: The cooling module or components of the cooling        module have disconnectable or pluggable interfaces for the        communication interfaces, the interfaces for connecting the        cooling circuits (coolants), and for the electrical interfaces.        For example, the cooling module or components thereof may be        configured as a 19″ plug-in component, wherein the lines for        communications, for the cooling liquid, and the electrical        terminals are connected automatically upon insertion.        Alternatively, it is possible to implement these lines via quick        release connections. In this way, a modular and easy maintenance        design is supported.        -   Communication interfaces: a communication interface, such as            Ethernet or LAN, connects the cooling module to the            management of the computing center, for example for            reporting the operational state of the cooling module or for            coordinating measures in case of a fault, e.g. a loss of            coolant. Furthermore, the cooling module may be connected            with the cooling circuits (for example, with the control of            the rack cooling circuit), and with the components (for            example servers) for coordinating and optimizing the supply            of cooling energy. A user interface may indicate the            operational state to the personnel of the computing center,            for example visually or acoustically.        -   Interfaces for cooling circuits: comprise the connections            between the cooling module or components thereof to the            cooling circuits according to the invention. The interfaces            may be configured as self-closing connections which prevent            or at least reduce leakage or dripping of the coolant fluid            from open conduits.        -   Electrical interfaces: These interfaces comprise all            interfaces for power supply and to the pumps, valves,            sensors and other components belonging to the cooling system            that are outside of the cooling module.        -   Mechanical interfaces: These interfaces include shapes,            dimensions and mounting elements of the cooling module,            which allow for a modular employment of the cooling module            or components thereof in the system for cooling a computing            system. For example, the cooling module or components            thereof may have a 19″ design, so that they may be attached            in a rack, similarly to servers or blade servers.            Furthermore, the mechanical interface may be designed such            that the cooling module or components thereof can be mounted            adjacent to one or more racks, while meeting the system            dimension of the racks.    -   Control of the pumps/valves/sensors/actuators: These components        include all components for driving the pumps, valves, sensors,        and actuators (e.g. power electronics for controlling the pumps        and valves, electronics to read the temperature sensors), both        for the cooling circuits of the computing system and for the        internal cooling circuit of the cooling module, as described in        FIG. 20.    -   Module for detecting a loss of coolant: This component is        illustrated in FIG. 37.    -   Heat exchangers: These components include the heat exchangers        for recooling, for free cooling, and for internal cooling.    -   Casing: The casing ensures compliance with the applicable safety        regulations depending on the design of the cooling module. Also,        the casing prevents (or may prevent), optionally by an        additional thermal insulation, that waste heat of the cooling        module, for example from the compressor motor or from power        electronics, is released to the outside, rather it ensures that        the cooling module is thermally neutral to the outside.    -   Emergency power supply: In the event of a power failure, an        emergency power supply, such as one based on an accumulator        battery, can maintain the operation of the cooling module for        some time and thus reduce the risk of overheating of the        computing system due to a power failure.    -   Moreover, a cooling module may be provided with a means for        removing condensate. In this way, the condensate resulting at a        cold spot of the cooling module and/or of a heat exchanger of        the computing system may be removed. Depending on the amount,        this may involve the evaporation of the condensate, for example        at the hot section of the refrigeration machine, or a discharge        of the liquid condensate.    -   Heating: In another embodiment, the cooling module comprises at        least one heating element for heating the computing system, for        example using a rack cooling circuit. This may be useful, for        example, in order to avoid an undesirably low temperature after        a shutdown of components or in case of a very low workload. In        this way, the risk of condensation in the racks or of such low        temperatures for which the components of the computing system        are not adapted may be reduced. Any cooling circuit may be used        for heating purposes. According to a further variation it is        possible to utilize the thermal energy of a cooling circuit to        heat another cooling circuit, for example the first cooling        circuit for processor cooling purposes may be connected to the        second circuit for rack cooling purposes, via a system of valves        and/or pumps, such that the first cooling circuit releases at        least part of its thermal energy into the second cooling        circuit, at least at times. Thus, less energy is needed for        heating, furthermore, an additional, usually electrical heating        element may be dispensed with.

FIG. 20 shows an exemplary embodiment of a cooling module 39 which mayfor example be attached at or in a server or rack (not shown).

Cooling module 39 comprises a housing 45 with a refrigeration machine 8and a controller 40 by which the cooling module is controlled.

Furthermore, cooling module 39 comprises a port 43 for processor coolingor for supplying a first cooling circuit.

Also, a port 44 is provided to which the rack cooling circuit may beconnected to provide a second cooling circuit.

As described in a previous embodiment, an intermediate heat exchanger 31is provided, which allows to combine process heat from refrigerationmachine 8 and heat from the first cooling circuit to be discharged viaport 41.

Cooling module 39 comprises an own internal heat exchanger 46 to coolthe cooling module. The air flow 47 is indicated by arrows. This coolingcircuit cools the waste heat of the cooling module itself. This wasteheat is generated by the components of the cooling module (for exampleby the motor of the compression refrigeration machine, or by thecontroller). Due to the internal cooling system of the cooling module,the cooling module is thermally neutral to the outside.

The cooling module may likewise be cooled using existing rack coolingmeans, for example an air circulation existing in the rack.

Furthermore, the cooling module comprises leak detection means 42 (amodule for detecting a loss of coolant), as described in FIG. 37, forexample in form of a pressure monitoring device and/or moisture sensor.

It will be understood that the cooling module 39 may comprise additionalcomponents, such as electronic interfaces and other cooling ports,mechanical connections, for example to be inserted into a 19″ racksystem, etc.

FIG. 20 a shows an exemplary embodiment of a cooling module 39 which maybe attached for example at or in a server or rack (not shown). Here, incontrast to FIG. 20, the additional component for free cooling isillustrated and will be explained with reference to the temperaturesindicated in the Figure.

Assuming a feed temperature at port 41 (recooling) of <20° C., forexample, as illustrated, and a feed temperature at port 44 (rackcooling) of 20° C., for example, the coolant may already be pre-cooledat the inlet of port 44, by heat exchanger 56, before being passed torefrigeration machine 8. Therefore, the coolant does not has to becooled from 20° C. to 15° C., i.e. by 5 K, by the refrigeration machine,but by 5K-ΔT. Thus, the cooling power to be provided by therefrigeration machine is reduced, and accordingly the energy consumptionfor cooling.

It will be understood that the principle of free cooling is not onlyapplicable in the cooling module, as illustrated, but in the entirecooling system according to the invention. Moreover, the principle offree cooling may be applied in combination with at least two, preferablyat least three cooling circuits, as illustrated in FIG. 13 a.

Referring now to FIG. 21, it will be explained how the cooling module 39is connected to a rack 20. The cooling module 39 is arranged close tothe rack 20 or is integrated into the rack 20.

Via a first port (43 in FIG. 20) a first cooling circuit 21 is supplied,which serves for processor cooling purposes. This cooling circuit is notconnected to the cold section of the refrigeration machine integrated incooling module 39.

In order to cool the air inside rack 20, a further cooling circuit 22 isprovided, which is connected to the second port of the cooling module(44 in FIG. 20).

Using this heat exchanger 24, the air within the rack is cooled. Coolingcircuit 22 is connected to the cold section of the refrigeration machineintegrated in the cooling module 39 (8 in FIG. 20).

Due to the internal cooling of the rack, the rack may be designed to bethermally neutral to the outside. Since the cooling module is alsothermally neutral to the outside, as described in FIG. 20, the entiresystem consisting of the rack and the cooling module is thermallyneutral to the outside. Therefore, this system does not require anyadditional cooling of the surrounding room.

FIG. 21 a shows a rack with a cooling module 39, as in FIG. 20, but withthe difference that the heat exchanger and the fans (not shown) forcooling the rack by means of heat exchanger 22 are configured as a rackcooling module 61 arranged adjacent to the rack, and that the air flowfor cooling purposes is fed through holes of the rack 20 and the rackcooling module 61. Rack 20, rack cooling module 61, and cooling module39 may be arranged one upon the other, as illustrated, or side by side(not shown), or in a combination thereof. Also, the cooling module 39may be part of the rack cooling module 61, or the rack cooling module 61may be part of the cooling module 39.

Referring to FIG. 22, the control of a cooling module will be explainedin detail. FIG. 22 shows a module which comprises a subset of thecomponents listed in FIG. 19.

The cooling module comprises a controller which is in particularresponsible for controlling the pumps and valves and for controllingtemperature and humidity sensors. Using this controller and theappropriate pumps and valves, the coolant is controlled, which forexample flows to a heat exchanger or to a refrigeration machine, etc.Therefore, the controller is connected with all components which aresupplied by the cooling module, for example via a network connection.

Moreover, the controller is connected to a leak controller including amoisture or pressure sensor, by means of which the pumps and/or thevoltage can be switched off, if necessary.

Furthermore, the cooling module is connected, via a network connection,with the computing system and with the individual sub-systems, such asindividual racks, means for power supply and telecommunications.

Referring to FIG. 23, the integration of a cooling module 39 in acomputing system will be described in more detail.

In this embodiment, cooling module 39 is positioned above the server 20and is in thermal communication with the server 20, as in FIG. 21.

The cooling module 39 comprises the refrigeration machine, a controller,valves, pumps and sensors, a heat exchanger through which the heat of afirst cooling circuit and the process heat from a refrigeration machineare combined and can be discharged through port 41.

Furthermore, the cooling module comprises a leak controller and aninternal cooling circuit.

A particular advantage thereof is that with this modular configurationonly the process heat has to be discharged to the outside via port 41.

Referring to FIG. 24, a system for cooling a computing system that isintegrated in a server 48 will be explained in greater detail.

The system comprises a refrigeration machine 8 integrated in the housingof server 48, in particular a compression-type refrigeration machine.

The cold section of compression refrigeration machine 8 supplies a coldliquid to a heat exchanger 24 arranged in the server, fans 50 generatean air flow in server 48, which is cooled in heat exchanger 24. Thetemperature may be maintained at about room temperature. Furthermore,instead of the fans, other means for producing a fluid motion may beused, for example means based on the principle of electro-hydrodynamics(not shown).

Through port 41 (feed and return flow), process heat of therefrigeration machine 8 is discharged to the outside.

Furthermore, a first group of heat generating components 34 is coupledwith a processor cooling circuit, via port 49 (feed and return flow).Through this processor cooling circuit, a large part of the energy isdischarged without the use of refrigeration machine 8.

Another group of heat generating components 36 is not coupled to aprocessor cooling circuit but is cooled by the cold air in the housingof server 48.

Referring to FIGS. 25 and 26, an exemplary embodiment will be explainedin which a cooling module is integrated in a blade server.

FIG. 25 shows a blade server 51. Blade servers are also known under thename BladeSystem or BladeCenter. The housing of the blade server has aplurality of slots for modules 52, so-called blades. These may be harddisks, memory chips, etc., for example.

Cooling module 39 is configured in correspondence with the modularconfiguration of the blade server and is likewise plugged-in. In thisexemplary embodiment, it occupies two slots of the blade server.

FIG. 26 shows the rear side of the blade server.

A refrigeration machine 8 provides cold cooling fluid which is suppliedto an internal heat exchanger 24 to cool the interior of the housing ofblade server 51.

Process heat from the refrigeration machine may be removed through thehot section and port 41.

Furthermore, modules 52 are provided with a processor cooling circuit.

The fluid of the processor cooling circuit does not need to be passedthrough refrigeration machine 8 but may be discharged through port 44.It is also conceivable to direct the fluid through the hot section ofrefrigeration machine 8, as with the above-described sequential cooling,or to thermally combine the processor cooling circuit with the dischargeof process heat, by means of an intermediate heat exchanger.

In this way only one port is needed for discharging the process heat.

FIG. 27 illustrates such a system with a plurality of blade servers 51.

The blade servers 51 comprise only one port for removing process heat.

Otherwise, as illustrated herein by way of example, the blade serversinclude, inter alia, a plugged-in cooling module as illustrated in FIGS.25 and 26, for example, and an internal second air-based coolingcircuit, as illustrated in FIG. 27 a. Outside the server, only onecooling circuit 53 is provided, through which heat (process heat) isdischarged to the outside, via heat exchanger 54.

FIG. 27 a illustrates a second, air-based cooling circuit for bladeservers, in which the air flow 62 is directed through heat exchanger 24.The blade server is designed such that this air flow 62 forms a closedair circulation within the blade server, so that the blade server is orcan be thermally neutral to the outside (except for the liquid-basedremoval of the process heat).

Referring to FIGS. 28 through 34, the different ways to integrate andarrange the cooling module, the computing system, and the controllerwill be illustrated.

FIG. 28 shows an embodiment in which a respective cooling module isdisposed on top of each rack.

FIG. 29 shows an embodiment in which one cooling module is arrangedabove two racks and therefore is responsible for cooling both racks.

It will be understood that instead of the two racks a plurality offurther racks may be added.

FIG. 30 shows an arrangement with a respective cooling module arrangedbelow each rack.

FIG. 31 shows an arrangement with a cooling module at a lateral side ofa rack. It is in particular conceivable that this cooling modulesupplies one or two racks with cold.

FIG. 32 shows an embodiment in which a cooling module is integrated inthe rack, for example as a plug-in module.

FIG. 33 shows an embodiment in which the controller of the coolingmodule is arranged separately from the actual cooling module. In thiscase, one controller is responsible for several cooling modules. Anadvantage of this embodiment of the invention is that the electroniccontrol device has to be provided only once.

FIG. 33 a shows an embodiment similar to that illustrated in FIG. 33, inwhich, however, the components of cooling modules are distributed to aplurality of cooling modules. So it is possible for example, that eachrack of the computing center has for example a first cooling moduleassociated therewith, each of which for example includes therefrigeration machine and other components of the cooling module forcooling the cooling circuits of the rack, while a second cooling moduleincludes the heat exchanger for recooling the process heat and combinesthe cooling circuits of several racks in this heat exchanger.

FIG. 34 shows a configuration in which a complete cooling moduleincluding a controller is integrated in each server or other module ofthe rack.

As can be seen from the legend, a rack may also be understood asanother, similar component of the computing system, for example atelecommunications device or a power supply device.

A server may likewise be understood as another module such as a harddisk module, etc.

Furthermore, components of the computing system as well as components ofthe system for cooling a computing system according to the invention maylikewise be accommodated in a container (not shown).

Referring to FIG. 35, another possibility of leak detection will bediscussed.

Shown is a fluid carrying conduit 54.

The fluid carrying conduit is surrounded by two electrodes 55, 56. Ifnow water penetrates into the region between electrodes 55 and 56, boththe capacity and the conductivity between the electrodes changes.

Using an appropriate controller, a leak can be deduced from theconductivity and/or from the capacity between the electrodes.

A similar system may be configured as a sheet structure, as shown inFIG. 36, where electrodes 55, 56 are spaced from each other by means ofa water permeable material, for example.

In this manner, the electrodes may be used as a part of the housing ormay be placed at the bottom of a rack or server, for example.

Again, a leak may be deduced based on conductivity and/or capacity.

Referring to FIG. 37, an embodiment of a module for detecting a loss ofcoolant (leak detection) will be described.

This module comprises means for detecting a loss of coolant and meansfor initiating an emergency stop.

As illustrated herein, the system may comprise a separate controllerwhich has communication interfaces, interfaces for reading sensors, andfor triggering actions as will be described below.

A loss of coolant may be detected based on coolant pressure monitoring(for example in a cooling system that is operated at a positivepressure), or using sensors which can detect liquids (capacitively orresistively, see FIG. 35 and FIG. 36), or based on an unexpectedincrease in temperature in the components of the computing system to becooled (temperature monitoring at or in the components to be cooled,such as processors), or based on the fact that coolant pumps run at ahigher speed due to a lack of medium to be pumped, or using flow metersthat monitor the amount of coolant flowing therethrough.

An advantage of using sensors which operate independently of theelectrical conductivity of the coolant (for example, pressure sensors)is that this permits to use coolants having a comparatively lowconductivity (for example below 2*10⁻⁸ S/m).

Preferably, a system including a plurality of means and sensors asdescribed above is distributed in and near the cooling module, theservers, racks, other components of the computing center such as powersupplies, and connecting lines for the coolant. In this way, in theevent of a leak the location of the leak can be determined.

The means of initiating an emergency shutdown may include acommunications interface through which components of the computingcenter and/or responsible personnel is informed about a loss of coolant.Furthermore, the means for emergency shutdown may in particular comprisemeans for interrupting the power supply of the concerned component (orcomponents) of the computing center (e.g. for the rack), and interfacesfor controlling or shutting down pumps and valves, by means of which theemergency shutdown as described below may be effected.

Furthermore, using a leak controller and an associated control system itis possible to determine which interventions must be taken to protectthe system (shutdown, partial shutdown, controlled or immediateshutdown).

For this purpose, the leak controller is connected to a switch of themain power supply for a server or a rack. Furthermore, the controllerhas a communications interface in order to generate a leak message,visually and acoustically, for example on the computing system or on ahigher-level control and monitoring system of the computing center,and/or to control other modules, or to co-ordinate a controlledshutdown.

Furthermore, the controller comprises a direct interface for controllingpumps and valves.

Depending on the size, location, and severity of the leak, a system maybe shut down in controlled manner, for example, or in the event of anemergency, may be abruptly disconnected from the power supply and shutdown.

For example, a situation may arise in which, though coolant is leaking,this does not present an immediate risk of damage to the computingsystem or its components yet. In this case, the computing system may beshut down in controlled manner and turned off, so that the runningapplications are closed and data is saved. Optionally, the applicationsand/or data may be relocated to other computing systems or componentsthereof which are not affected by the loss of coolant. With suchcontrolled shutdown it can be ensured that an interruption of coolantflow does not result in a local overheating in the components connectedto the cooling circuit.

The system for detecting loss of coolant may receive a command foremergency stop through the communication interface. With this emergencystop, the entire computing system or portions of the computing systemmay be disconnected from power supply, for example, and/or the pumps forcirculating the coolant may be switched off. In this way, possibledamage to components of the computing system or computing center causedby cooling water can be avoided or reduced. Further, it is conceivablethat the emergency shutdown involves a pump by which, in case a loss offluid is detected, a negative pressure is generated in the coolantsystem. For example, the pump may pump out the liquid into a designatedreservoir or into drains. Due to the resulting negative pressure, no oronly little additional water will leak, so that the damage in the systemwill remain localized. Furthermore, the cooling fluid conduits may beclosed using valves, whereby further liquid can be prevented fromleaking from the system.

There may also arise a situation in which an immediate danger of damageto the computing system cannot be excluded. In this case, disconnectionof the power supply and the pumps may be effected immediately, withoutpreviously shutting down the computing system in controlled manner andwithout closing the running applications and securing the data.

In another embodiment of the invention, means for emergency shutdown areintegrated in or adapted to a rack or other component of the computingsystem.

Especially in the case where the cooling system is configured as anintegrated or adapted module, the shutdown of the cooling module and ofthe component of the computing system or computer center made beeffected locally, if necessary, without affecting other components ofthe computing system or computing center.

The procedure of shutting down and switching off is illustrated in theflow charts of FIG. 38 and FIG. 39.

FIG. 38 illustrates a controlled shutdown.

As soon as a leak is detected in a rack, the computing center will beinformed via an electronic interface.

The computing center will then distribute applications that run in thesection affected by the leakage to other parts of the system which arenot affected by the leakage. Also, the data is backed up.

Subsequently, the affected system is shut down and then separated fromthe power supply.

In case of an emergency shutdown, for example due to a major release ofwater, the power supply for a rack is disconnected immediately(immediate shutdown), as shown in FIG. 39. Since in this example thecooling module which includes the leak controller will be shut downimmediately too, there will be no notification to the computing centervia an electronic interface.

FIG. 40 schematically illustrates an embodiment of a computing center55.

Computing center 55 comprises a plurality of racks 20 which in turncomprise individual modules 52, such as servers, hard disk units, etc.

In this embodiment, modules 52 are coupled by liquid-based cooling to afirst cooling circuit 21, through which heat is discharged to theoutside via heat exchanger 23.

A second cooling circuit 22 with a lower feed flow temperature, whichcools the components of the rack by an internal air circulation, issupplied from a refrigeration machine 8. For this purpose, a heatexchanger is provided within the racks 20.

With respect to the individual racks, the first cooling circuit 21 iscombined and the second cooling circuit 22 is combined. This may beimplemented through connection of heat exchangers 24 to cooling circuit22 by connecting them in parallel to cooling circuit 22. It is alsoconceivable for the heat exchangers 24 to be connected in succession, sothat the cooling fluid flows from one heat exchanger to the next (notshown).

Using another external heat exchanger 25, process heat from the hotsection of the refrigeration machine is discharged.

FIG. 41 shows another exemplary embodiment of a computing center 55.

Unless otherwise stated, computing center 55 is similar to that of theexemplary embodiment illustrated in FIG. 40.

In contrast to FIG. 40, the first cooling circuit 21 for processorcooling purposes is in thermal communication with the cooling circuit ofthe hot section of the refrigeration machine 8, through a heat exchanger31.

This is possible, because the cooling circuits have a similartemperature.

An advantage of this embodiment of the invention is that consequentlyonly one port has to be provided for discharging waste heat through heatexchanger 25.

FIG. 42 shows another embodiment of the invention which is based on thatof FIG. 41.

In contrast to FIG. 41, a respective refrigeration machine is providedfor each rack 20.

The waste heat sections of the refrigeration machines are combined.

FIG. 43 shows another embodiment of a computing center 55, in whichservers 20 are connected to a cooling module 39 (as described above).

The advantage of this embodiment is that for extracting energy from thesystem, the cooling modules only have to be connected to cooling circuit53 through which heat is discharged to the outside via heat exchanger25. It will be understood that this heat may be used as useful heat.

FIG. 44 shows an embodiment of the invention in which a plurality ofservers 37 are included in a rack 20, and in which a cooling circuit ofservers 37, which for example is a processor cooling circuit, iscombined across multiple servers to a first cooling circuit 21, whereinthe volume flow of cooling liquid can be controlled individually foreach server using a respective pump 57 and, optionally, an additionalvalve 33. Heat is transferred to the environment via recooling heatexchanger 23. Pumps 57 and, optionally, valves 33 may be controlled in amanner as required by the respective processor cooling circuit in theservers, for example based on an evaluation of temperature sensors (notshown). This allows the volume flow of the coolant in the respectiveservers to be regulated to the required amount, furthermore, theperformance of the pumps may be optimally adapted to the required level,and the temperature difference between inlet and outlet of the processorcooling circuits may be controlled through the controllable oradjustable volume flow, for a given amount of heat to be discharged. Itwill be understood that this adjustment of the volume flow is alsoapplicable to more cooling circuits, for example cooling circuits 21,22, and 38 as illustrated in FIG. 13.

FIG. 45 shows a configuration in which a plurality of racks 20 areprovided, and in which a cooling circuit for servers 37, which forexample is a processor cooling circuit, is combined across multipleservers to a first cooling circuit 21, wherein the volume flow ofcooling liquid can be controlled individually for each server using avalve 33, and wherein the volume flow for each rack is controlled by apump. Thus, the volume flow may be set and controlled separately foreach rack 20 and for each server 37. It will be understood that thisadjustment of the volume flow is also applicable to more coolingcircuits, for example cooling circuits 21, 22, and 38 as illustrated inFIG. 13.

FIG. 46 shows another embodiment of the invention in which a rack 20 isequipped with individual modules that are illustrated as servers 37, andin which a cooling circuit is a processor cooling circuit, for example.In contrast to the embodiments illustrated above, a bypass 58 isprovided for each server, via which cooling fluid may be directed pastthe server detouring it, using a valve 33 or a T-shaped branching. Bymeans of a controllable bypass, a portion of the coolant which flowsthrough the modules, may be returned in a circuit from the coolantoutlet of servers 37 to the coolant inlet of servers 37 without beingpassed via the processor cooling port 21 of the rack and the recoolingheat exchanger 23. This allows to increase the amount of coolant flowingthrough the server, and so the temperature difference between coolantoutlet and coolant inlet of the server may be reduced without any needto increase the flow rate of recooling heat exchanger 23. The bypass mayfor example be controlled in function of the individual work load of theserver and/or the individual temperature of the server, so that theindividual server may influence the temperature at its coolant outletand coolant inlet in function of the work load. This may be relevant inconjunction with an optimal design of the cooling system of anindividual computing center (for example, for adapting the coolanttemperatures, avoiding low temperatures due to large temperaturedifferences and thus preventing condensation, dimensioning of flowrates).

Furthermore, the bypass and the so allowed increase of the amount ofcoolant flowing through the server permit to achieve a more homogeneoustemperature distribution among all the components connected to theprocessor cooling circuit.

In case of an operating state, for example, in which only one componentout of a plurality of components connected to the processor coolingcircuit of a server generates much heat energy to be dissipated, and theother components very little, overheating of this component may beprevented by increasing the flow rate of the coolant in the individualserver without influencing the coolant flow rate of the overall system.

In this way, the system may adapt to changing computational loads oroperating conditions by controlling the cooling fluid in the bypass.

The bypass and the amount of cooling liquid flowing through the bypassmay be adjusted by means of controllable valves and controllable pumps.Controlling (not shown) may be accomplished by the server or fromoutside the server, and temperature sensors (not shown) may also beinvolved.

It is also possible to provide a bypass across an entire rack insteadfor individual servers (not shown), for example across heat exchangers24 of the second cooling circuit 22 or another system of the computingcenter (for example a power supply). The operation thereof correspondsto that of a bypass across a server.

It will be understood that the bypass is also applicable to more coolingcircuits, for example cooling circuits 21, 22, and 38 as illustrated inFIG. 13.

FIG. 47 shows another embodiment of the cooling system including abypass similarly to that illustrated in FIG. 46, but with the differencethat the cooling liquid is not returned from the outlet of the processorcooling circuit of server 37 to the inlet of the processor coolingcircuit of server 37, rather cooling liquid is directed past the serverdetouring it. In this way, the volume flow in the coolant circuit forcooling the processor may be reduced without affecting the volume flowin recooling heat exchanger 23. Another advantage of this bypass is thatit allows to reduce a pressure loss in servers with low work load.

A cooling system in the sense of the invention may consist of a numberof cooling circuits which may be connected together in different ways.As for example illustrated in FIG. 9 and in FIG. 13 a, these coolingcircuits may be connected to form a circuit in which the differentindividual cooling circuits are connected in series, wherein theindividual cooling circuits connected in series have a differenttemperature level (provided that each of these individual circuitsabsorbs thermal energy), but the volume flow in all cooling circuitsconnected in series is identical. Each cooling circuit is affected by apressure loss which adds up in cooling circuits connected in series andwhich has to be compensated for by the pumps of the cooling circuit. Incase a module (such as a server) of the coolant circuit, or a pluralityof modules (for example servers) has/have a lower work load and lessthermal energy to be discharged, the described bypass permits toindividually reduce the volume flow of coolant in the server with lesswork load without thereby reducing the volume flow in the other serversconnected in series. Since a bypass usually exhibits a significantlylower pressure loss than the cooling circuit in a module (because thebypass extends over short lengths of coolant conduits, while in amodule, for example in a server, the cooling circuit extends over longerconduits lengths, for example via multiple processors or other powercomponents) the pressure loss to be compensated for by the pumps andthus the required pumping capacity will also be reduced. In this way,the described bypass permits to adapt the required pumping capacity tothe individual thermal load to be cooled in each of the modules cooledby cooling circuits, for example servers, in function of the design andconfiguration of the cooling system.

A bypass may also be provided across an entire rack, for example acrossheat exchangers 24 of the second cooling circuit 22, or across anothersystem of the computing center (for example a power supply) instead forindividual servers (not shown). The operation thereof corresponds tothat of a bypass across a server.

FIG. 48 shows another embodiment of the invention, which is based onthat of FIG. 40. In contrast to FIG. 40 it is illustrated by way ofexample that the refrigeration machine is not located in the computingcenter but outside, here illustrated adjacent to heat exchangers 23, 25,and 56.

As another difference to FIG. 40, free cooling is illustrated, with thecooling fluid of the second cooling circuit 22 first being passedthrough free cooling heat exchanger 56, before being fed to the inlet 14of the cold section 16 of refrigeration machine 8. Thereby, the coolingfluid is cooled at heat exchanger 56 by an amount of ΔT, depending,inter alia, on the ambient conditions (e.g. temperature), thus reducingthe cooling power to be provided by refrigeration machine 8 and hencethe energy consumption thereof. Depending on the ambient conditions ofheat exchanger 56, the full cooling capacity for the second coolingcircuit 22 may possibly be provided by free cooling, for example in caseof low ambient temperatures of, for example, less than 10° C.

FIG. 49 shows another exemplary embodiment of the invention which isbased on that of FIG. 40. In contrast to FIG. 40, here, the secondcooling circuit is connected to a cold water supply 63 which is madeavailable to the computing center. This cold water supply may forexample be supplied with cooling energy by a refrigeration machine notlocated in the computing center, or by an ordinary water supplyconnection, or by a geothermal cooling system.

FIG. 50 schematically illustrates another exemplary embodiment of acomputing center 55 which involves recovery of electric energy fromthermal energy.

Computing center 55 comprises a plurality of racks 20 which in turncomprise individual modules 52, such as servers, hard disk units, etc.

In this embodiment, modules 52 are in thermal communication with a firstcooling circuit 21, via liquid-based cooling.

A second cooling circuit 22 with a lower feed flow temperature, whichcools the components of the rack in an internal air circulation, issupplied by a refrigeration machine 8. For this purpose, a heatexchanger is provided within rack 20. This cooling circuit is only shownin phantom here, the cooling circuit is not shown.

With respect to the individual racks, at least the first cooling circuit21 is combined.

The exemplary embodiment comprises a thermoelectric generator, orPeltier element 66. The first cooling circuit with a feed flowtemperature T1 first extends to a heat exchanger (hot side) 67 of anelement for generating electric energy, which is in thermalcommunication with one side of thermoelectric generator 66. Another heatexchanger (cold side) 68 of the element for generating electric energyis in thermal communication with the other side of thermoelectricgenerator 66, the return flow temperature of this heat exchanger (coldside) 68 being T2. The heat exchanger (cold side) 68 is in thermalcommunication, through a cooling circuit, with recooling heat exchanger25.

Thus, the temperature difference at thermoelectric generator 66 isΔT=T1−T2. In this manner, electric energy is generated, which in thisembodiment is fed as recycled energy 70 via an inverter 69 into thepower supply, so that the electric energy required for the power supplyof the computing center 65 is reduced by the recycled energy 70,assuming that an approximately constant amount of energy is provided topower the components of the computing center 64.

Thus, thermal energy may be converted into electric energy which issupplied to the computing center, thereby reducing the amount ofelectric energy required for the power supply of a computing center.

Moreover, the amount of thermal energy to be discharged by recoolingheat exchanger 25 is reduced, which results in reduced operating costsfor the heat exchanger.

It will be understood that other physical effects for generatingelectric energy from thermal energy or based on a temperature differenceΔT may likewise be used; for example, instead of thermoelectricgenerator 66, a mechanical generator based on the Carnot cycle may beused, for example, an ORC (organic rankine cycle) machine which drivesan electric generator to produce energy. Also, a Stirling engine may beused. Moreover, a thermo-magnetic generator may be used.

Since in some physical processes for converting thermal energy into adifferent form of energy, the efficiency thereof is proportional to thetemperature difference ΔT provided (for example in the Carnot cycle),the system according to the invention for cooling a computing systemwhich provides a first cooling circuit with a high temperature permitsor at least better promotes a conversion of thermal energy from acomputing center into electric energy.

The invention enables to considerably reduce the power consumptionrequired to cool a computing system.

LIST OF REFERENCE NUMERALS

-   1 System for cooling a computing system-   2 Feed flow first cooling circuit-   3 Return flow first cooling circuit-   4 Inlet second cooling circuit-   5 Outlet second cooling circuit-   6 Liquid-cooled components-   7 Air-cooled components-   8 Refrigeration machine-   9 Evaporator-   10 Compressor-   11 Condenser-   12 Expansion valve-   13 Coolant circuit of compressor unit-   14 Inlet-   15 Outlet-   16 Cold section-   17 Inlet-   18 Outlet-   19 Hot section-   20 Rack-   21 First cooling circuit-   22 Second cooling circuit-   23 Heat exchanger (recooling)-   24 Heat exchanger (rack cooling)-   25 Heat exchanger (recooling)-   26 Module-   27 Fan-   28 Port-   29 Port-   30 Computing system-   31 Heat exchanger-   32 Cooling circuit hot section-   33 Valve-   34 First group of heat generating components-   34 Second group of heat generating components-   36 Third group of heat generating components-   37 Server-   38 Third cooling circuit-   39 Cooling module-   40 Controller-   41 Port (recooling)-   42 Leak detection-   43 Port processor cooling-   44 Port rack cooling-   45 Housing-   46 Heat exchanger-   47 Air circulation-   48 Server-   49 Port-   50 Fan-   51 Blade server-   52 Module-   53 Cooling circuit-   54 Conduit-   55 Computing center-   56 Heat exchanger (for free cooling)-   57 Pump-   58 Bypass-   59 Heat exchanger of refrigeration machine-   60 Coolant ports-   61 Rack cooling module-   62 Air flow of blade server-   63 Cold water supply-   64 Electric energy to power components of the computing center-   65 Electric energy to power the computing center-   66 Thermoelectric generator, Peltier element-   67 Heat exchanger for element for generating electric energy, hot    side-   68 Heat exchanger for element for generating electric energy, cold    side-   69 Inverter-   70 Recycled electric energy

1. A system for cooling a computing system, comprising a refrigerationmachine, wherein the computing system comprises at least a first and asecond cooling circuit, and wherein said first cooling circuit isoperable using a liquid or via heat conduction, and wherein at leastsaid second cooling circuit is connected to a cold section of therefrigeration machine.
 2. The system for cooling a computing system asclaimed in claim 1, wherein a return flow of the first cooling circuitis connectable both to a heat exchanger and to the cold section of therefrigeration machine.
 3. The system for cooling a computing system asclaimed in claim 2, wherein a return flow of the second cooling circuitis connectable both to a heat exchanger and to the cold section of therefrigeration machine.
 4. The system for cooling a computing system asclaimed in claim 1, wherein the system comprises at least three coolingcircuits, one cooling circuit of which being operated by air and the twoother cooling circuits being operated using a liquid, wherein at leastone cooling circuit of the other cooling circuits being connectable bothto an external heat exchanger and to a cold section of the refrigerationmachine.
 5. The system for cooling a computing system as claimed inclaim 1, wherein the first cooling circuit and the hot section of therefrigeration machine each include a heat exchanger which are in thermalcommunication with each other through a further heat exchanger, andwherein waste heat from the two cooling circuits is dischargeablecollectively.
 6. The system for cooling a computing system as claimed inclaim 1, wherein the refrigeration machine is a compression-typerefrigeration machine or a sorption refrigeration machine, absorptionrefrigeration machine and/or a refrigeration machine operating on theprinciple of absorptive dehumidification (DCS), a refrigeration machineoperating on the thermoelectric effect, or a refrigeration machineoperating on the magnetocaloric principle, or a geothermal refrigerationmachine, or a refrigeration machine operating with Peltier elements, ora steam jet refrigeration machine, or a refrigeration machine operatingon the Joule-Thomson effect, or a refrigeration machine operating on theprinciple of evaporative cooling.
 7. The system for cooling a computingsystem as claimed in claim 1, wherein racks or processors or powercomponents of the computing system can be cooled using a liquid.
 8. Thesystem for cooling a computing system as claimed in claim 1, wherein thesystem comprises means for selectively distributing the cooling fluidwithin the computing system.
 9. (canceled)
 10. The system for cooling acomputing system as claimed in claim 1, wherein the system comprisescontrol electronics with an interface for connecting the computingsystem.
 11. The system for cooling a computing system as claimed inclaim 1, wherein the system comprises a cooling module whichaccommodates at least the refrigeration machine and an electroniccontroller.
 12. The system for cooling a computing system as claimed inclaim 11, wherein the feed flow temperature of the first cooling circuitdiffers by at least 20° C. from the feed flow temperature of the secondcooling circuit.
 13. The system for cooling a computing system asclaimed in claim 11, wherein the first cooling circuit is coupled withprocessors or power components of the computing system.
 14. The systemfor cooling a computing system as claimed in claim 1, wherein a heatexchanger of the first cooling circuit or a heat exchanger connectedwith a hot section of the refrigeration machine is connected to theheating system of a building, to a hot water supply, or a powergenerator.
 15. The system for cooling a computing system as claimed inclaim 1, wherein the refrigeration machine is integrated into a rack ora server, in particular a blade server, or into other components (powersupplies, telecommunications), or is arranged directly adjacent to aserver or to a rack.
 16. The system for cooling a computing system asclaimed in claim 1, wherein a liquid of the second cooling circuit,after having passed through a cold section of the refrigeration machine,can be fed via a heat exchanger for cooling the air inside the computingsystem, and wherein the liquid, after having passed through the heatexchanger, can be fed into the first cooling circuit.
 17. (canceled) 18.The system for cooling a computing system as claimed in claim 1, whereinthe system comprises processor cooling means, and wherein processors,RAMs, chip sets, memory devices, graphic components, power components ofpower supplies, power components of uninterruptible power supplies,power supplies, telecommunications devices, or hard disks are connectedto a processor cooling circuit.
 19. The system for cooling a computingsystem as claimed in claim 1, wherein the computing system and therefrigeration machine are arranged in one room, wherein in particularthe refrigeration machine is integrated into a component of thecomputing system, or is arranged adjacent to a component of thecomputing system, and wherein there is no air conditioning provided tocool the air in the room.
 20. The system for cooling a computing systemas claimed in claim 1, wherein the system comprises means for emergencyshutdown in the event of a loss of coolant.
 21. The system for cooling acomputing system as claimed in claim 1, wherein said means for emergencyshutdown include means for determining the severity or the location ofthe possible risk of coolant loss, and wherein based thereon themeasures of emergency shutdown can be defined, in particular theemergency shutdown can be limited to an affected section of thecomputing system. 22-23. (canceled)
 24. The system for cooling acomputing system as claimed in claim 1, wherein the system comprises aplurality of cooling circuits, of which one cooling circuit is coolablewithout using the refrigeration machine, and wherein another coolingcircuit is coolable using a refrigeration machine.
 25. The system forcooling a computing system as claimed in claim 1, wherein the systemcomprises a plurality of cooling circuits, of which at least two coolingcircuits are in thermal communication with each other and thus combinedto form one circuit.
 26. (canceled)
 27. The system for cooling acomputing system as claimed in claim 1, wherein the system comprises aplurality of cooling circuits, wherein a bypass is provided in at leastone cooling circuit, by means of which the volume flow in the module tobe cooled and connected to the cooling circuit can be increased by apartial recirculation of the coolant without increasing the total volumeflow of the coolant in the cooling circuit. 28-44. (canceled)
 45. Acomputing system, comprising a housing in which components of thecomputing system are arranged, wherein the computing system comprises atleast a first and a second cooling circuit, wherein the first coolingcircuit provides for cooling processors and power components of thecomputing system using a liquid or by heat conduction, and wherein thesecond cooling circuit comprises a heat exchanger arranged in saidhousing. 46-57. (canceled)
 58. A method for cooling a computing system,wherein the computing system comprises at least a first and a secondcooling circuit, wherein the first cooling circuit is operated at ahigher temperature than the second cooling circuit and using a liquid orby heat conduction, and wherein at least the second cooling circuit isoperated through a cold section of a refrigeration machine. 59-62.(canceled)